The present embodiments relate to imaging with an intra-patient probe.
In many cases, different imaging modalities are used simultaneously or consecutively on the same patient. Multiple modalities may be used where one modality is primarily used to guide the positioning of surgical tools while another modality is used to provide diagnostic images. Multiple modalities may be used to acquire different diagnostic information. Imaging modalities include optical, optical coherence tomography, magnetic resonance, computed tomography, ultrasound, x-ray, positron emission tomography, or single photon emission computed tomography. Different modalities visualize different properties of tissue or are available for different procedures. Some of the modalities may include a sensor or scanner in an intra-patient probe, such as optical, ultrasound or magnetic resonance modalities. Other modalities, such as ultrasound, computed tomography, magnetic resonance, or x-ray, may be used to detect an intra-patient probe.
For multi-modality imaging, the relative position of the regions represented by the corresponding images may be aligned or registered. To enable co-registration of images acquired by different imaging systems, the geometric relationship between the imaging systems is established. In some embodiments, the spatial relationship between the imaging systems and the object (e.g., the catheter) is established, such as where the imaging with the different systems is not simultaneous.
Various approaches are used to register the modalities for image alignment. Positions and orientation sensors may provide position and orientation of one imaging system in a coordinate system of another imaging system. However, position sensors are costly and not compatible with some imaging modalities.
In another approach for registration, markers attached to one imaging system may be imaged by the other imaging system in order to determine position and orientation of one imaging system in the coordinate system of the other imaging system. For example, radio opaque markers are provided in imaging catheters. Such markers may be used for tracking the imaging catheter in a fluoroscopic image. While finding the approximate position of the markers in the fluoroscopic imaging plane is a lesser problem, determining the rotation angles is challenging. One marker, bone or other structure may, at least partially, occlude another marker, making position determination difficult or impossible. Determining the position or depth along the X-ray beams is an error-prone measurement. The depth of the markers position along the X-ray beams may affect scaling, resulting in ambiguity.
In another approach to registration, images acquired by one imaging system may be matched to images acquired by the other imaging system. However, images from different modalities may be difficult to match due to differences.